Affixable armor tiles

ABSTRACT

Affixable armor that can be used to provide additional protection for a surface is described. The affixable armor includes polygonal ceramic tiles that can be attached directly to a surface, or first attached to a carrier sheet which is then attached to a surface. A visco-elastic polymer can be used to help absorb projectile impact. The ceramic tiles include a substantially conical or pyramidal deflecting front surface to provide additional protection. The ceramic tiles can be placed so that they are spaced to provide a gap with a width that is less than the diameter of an expected ballistic threat in order to provide additional projection. The affixable armor can be configured for rapid removal and replacement, or it may be permanently affixed to the surface.

CONTINUING APPLICATION DATA

This application claims the benefit of U.S. Provisional Application No. 60/909,152, filed Mar. 30, 2007, and U.S. Provisional Application No. 60/910,998, filed Apr. 10, 2007, both of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to composite armor. More specifically, the invention relates to composite armor that can be readily affixed to a surface and/or includes spaced armor tiles.

BACKGROUND OF THE INVENTION

Currently a majority of high mobility multi-purpose wheeled vehicles (HMMWV; more commonly referred to as Humvees) are fitted with metallic armor. However, with increasing lethality and availability of armor piercing ballistic projectiles of improvised explosive devices (IEDs) such as explosively formed penetrators and more potent land mines, it is becoming difficult to provide additional armor protection without exceeding prohibitive weight limitation.

Composite materials have been prepared for use as lightweight armor for lighter fighting vehicles. For example, the composite material HJ1, a phenolic-resin based polymeric matrix with high-strength S-2 glass-fiber reinforcement, has been used to reinforce Humvee armor. However, relatively simple fiber-based composite armors such as HJ1 have difficulty protecting vehicle occupants against many common ballistic and blast threats, such as armor piercing (AP) ammunition.

Armor piercing (AP) ammunition is designed to penetrate the hardened armor of modern military vehicles. Studies indicate that AP ammunition, which typically includes a sharp, hardened penetrator, tends to move the fibers within the composite laterally away from the advancing projectile, resulting in kinked fibers around the penetration cavities but with little energy absorption. Thus, fiber-based composite armor is relatively ineffective against AP ammunition because neither the fiber nor the polymer matrix is hard enough to cause deformation of the penetrator.

Ceramic faced armor systems were thus developed to defeat armor piercing (AP) ammunition by breaking up the projectile in the ceramic material and terminating the fragment energy in the backing plate that supports the ceramic tiles. During impact, the projectile is blunted and cracked or shattered by the hard ceramic face. However, the armor system is typically damaged as well. Armor systems containing segmented ceramics in the form of “tiles” help address this problem by decreasing crack propagation to adjacent tiles. However, strong stress waves can still damage tiles adjacent to the impacted tile by propagating through the edges of the impacted tile and into adjacent tiles.

Efforts have been made to minimize the damage to adjacent tiles resulting from blast or projectile impact. See U.S. patent application Ser. No. 11/656,603, the disclosure of which is incorporated herein by reference. Providing gaps of a certain size between the ceramic tiles can help decrease damage to adjacent tiles, but it can also provide regions of the armor that are more vulnerable to penetration.

For both initial armor installation and the repair of damaged armor sections it is important to be able to provide armor to vehicles or other structures quickly and efficiently. One effort to address this problem is represented by the rubber-encased ceramic appliqué armor tiles developed by Ceradyne Inc. (i.e., RAMTECH™ armor), described in U.S. Pat. No. 6,532,857. Another effort in which armor tiles are attached to a surface using hook-and-loop fasteners was developed by Foster-Miller, Inc. (i.e., LAST® armor), and is described in U.S. Pat. No. 5,170,690. However, there remains a need for vehicle armor that provides excellent vehicle protection while enabling quick and efficient installation.

SUMMARY OF THE INVENTION

The invention provides for a light weight, non-flat ceramic tile of varying thickness according to threat level with hollow back, raised edges, absorbing backing and spacing to uniquely defeat high energy hardened and explosively formed projectiles in minimal thickness and weights. In one aspect, the present invention provides an affixable armor sheet that includes a plurality of adjacent polygonal ceramic tiles that include a base, sides, and a substantially conical or pyramidal deflecting front surface. The tiles are on a carrier sheet with a front side and a back side. The affixable armor sheet includes attachment means for attaching the base of the polygonal ceramic tiles to the front side of the flexible carrier sheet.

The affixable armor sheet includes a variety of different embodiments. For example, the back side of the carrier sheet can include an adhesive. Alternately, or in addition, the attachment means can include an adhesive. In another embodiment, the attachment means include a mechanical fastener. In yet another embodiment, the ceramic tiles are encased in a retaining polymer. In a further embodiment, a shock absorbing material is provided on the base of the ceramic tiles.

Further embodiments of the affixable armor sheet relate more to the ceramic tiles and their placement. For example, in one embodiment, the ceramic tiles include a cavity containing a fire-retarding material. In another embodiment, the deflecting front surface of the ceramic tiles includes a ridge that flares upwards above the sides of the ceramic tiles. In further embodiments, the ceramic tiles are spaced apart by a gap that may have a width that is substantially less than the diameter of an expected ballistic threat, less than 2 millimeters, or less than or equal to 0.25 millimeters. Finally, in a further embodiment, where an affixable armor sheet is placed on each of two surfaces that meet at an angle, one or more gap-filling ceramic tiles can be positioned between the two affixable armor sheets and over the intersection of the two surfaces.

In another aspect, the present invention provides a composite armor sheet that includes a layer of adjacent polygonal ceramic tiles that include a base, sides, and a front surface encased in a retaining polymer positioned over a carrier sheet, wherein the ceramic tiles are spaced apart by a gap with a width that is less than the diameter of an expected ballistic threat. In additional embodiments, the gap has a width that is less than half the diameter of the expected ballistic threat, less than 2 millimeters, or less than or equal to 0.25 millimeters.

Embodiments of this aspect of the invention can include various different types of ceramic tiles. For example, in one embodiment, the ceramic tiles include a cavity containing a fire-retarding material. In another embodiment, the ceramic tiles include a cavity positioned on the back of the ceramic tile that deforms upon projectile impact to decrease damage to the vehicle and/or adjacent ceramic tiles. In a further embodiment, the ceramic tiles have a non-spherical deflecting front surface. Tiles include a non-spherical deflecting front surface may also, in some embodiments, have a portion of the deflecting front surface of the ceramic tiles that is substantially conical or pyramidal, and/or a deflecting front surface that includes a ridge that flares upwards above the sides of the ceramic tiles.

Unless otherwise specified, “a,” “an,” “the,” and “at least one” are used interchangeably and mean one or more than one.

Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” and “right,” are for illustrative purposes only and can be varied within the scope of the disclosure.

BRIEF DESCRIPTION OF THE FIGURES

The following figures illustrate various aspects of one or more embodiments of the present invention, but are not intended to limit the present invention to the embodiments shown.

FIG. 1 provides a cross-sectional view of an affixable armor sheet.

FIG. 2 is a top plan view of an affixable armor sheet.

FIG. 3 is an exploded perspective view of a mechanical fastener suitable for attaching the polygonal ceramic tiles to a carrier sheet.

FIG. 4 is a side view of adjacent affixable armor sheets connected by sheet connectors.

FIG. 5 is a side view of a vehicle with affixable armor sheets mounted to the vehicle by straps.

FIGS. 6A and 6B provide top perspective and bottom perspective views, respectively, of a polygonal ceramic tile.

FIGS. 7A and 7B provide cross-sectional and a top perspective views, respectively, of a polygonal ceramic tile that includes a flared perimeter.

FIG. 8 is a cross-sectional view of affixable armor sheets positioned along an angled surface with a gap-filling ceramic tile positioned between the armor sheets

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention provides an affixable armor sheet that includes a plurality of adjoining polygonal ceramic tiles. Affixable, as used herein, refers to the ability of the armor sheet to be attached to a surface in either a reversible or non-reversible manner. Because the armor sheet is affixable, the armor sheet of the present invention can be used to upgrade and/or retrofit the armor of a vehicle or structure to provide an increased ability to defeat incoming ballistic threats in addition to its use as a base armor.

An embodiment of the affixable armor sheet 10 of the present invention is shown in FIG. 1, which provides a cross-sectional view of an affixable armor sheet 10. The armor sheet 10 includes a plurality of adjacent polygonal ceramic tiles 12. The ceramic tiles 12 form a protective layer of ceramic tiles 12 that can stop or deflect an incoming projectile that strikes the ceramic tiles 12. The ceramic tiles 12 are adjacent to one another and may fit together without gaps, or they may include gaps 14 between the tiles.

The affixable armor sheet 10 also includes a carrier sheet 16. The carrier sheet 16 includes a front surface 18 and a back surface 20. The ceramic tiles 12 are attached to the front surface 18 of the carrier sheet 16. The back surface 20 of the carrier sheet 16 is positioned over a surface of the vehicle 22 or other structure that the affixable armor sheet 10 is intended to protect. In addition to connecting and supporting ceramic tiles 12, the carrier sheet 16 may also provide additional protection. After the ceramic tiles 12 shatter and deflect fragments of an incoming projectile over a broader area, the carrier sheet 16 may have sufficient strength to decelerate the fragments and prevent penetration. The kinetic energy released during this process is absorbed through a variety of mechanisms, including fiber/wire strain and fracture, fiber/wire pullout, and composite delamination. Because the carrier sheet 16 also provides additional protection, the affixable armor sheet 10 may be referred to as a composite armor sheet.

The carrier sheet 16 can be a flexible material to facilitate placement of the affixable armor sheet 10 on surfaces that are curved or include other irregularities. While the ceramic tiles 12 are typically hard and inflexible, placing them on a flexible carrier sheet 16 and including gaps 14 between the ceramic tiles 12 will allow the affixable armor sheet 10 itself to be fairly flexible overall. Use of a flexible carrier sheet 16 also more easily allows for the inward deflection of the tiles 12, particularly when the armor sheet includes gaps 14, which enables the affixable armor sheet 10 to present a greater thickness of ceramic material to an incoming projectile.

Examples of flexible material suitable for inclusion in a flexible carrier sheet 16 include fiberglass cloth, ballistic nylon cloth, fiber-reinforced polymer, metallic film, and elastomers (e.g., rubber). The flexible carrier sheet 16 is generally a relatively thin sheet of material to minimize weight and enable greater flexibility. For example, it may have a thickness of about 1/16^(th) to about ¼^(th) of an inch. The flexible carrier sheet 16 can be provided in any suitable size. For example, the flexible carrier sheet 16 may have a length and/or width of about 0.5, 1, 2, or 3 feet, providing a square or rectangular shape. Furthermore, the flexible carrier sheet 16 can be provided as a standard size (e.g., 1′×1′ square sheets) or it may be provided in specific shapes and sizes to protect a portion of the surface upon which it will be placed. A top plan view of an affixable armor sheet 10 is provided in FIG. 2. While the affixable armor sheet 10 can include a flexible carrier sheet 16, non-flexible carrier sheets 16 can also be used. If the carrier sheet 16 is not flexible, it can be formed from relatively non-flexible epoxy resins, thermoset plastics, metals, fiber-glass, and/or metal wire reinforced polymers.

The ceramic tiles 12 are attached to the front surface 18 of the carrier sheet 16 by various attachment devices such as a tile backing layer 26 and/or a mechanical fastener 28. The tile backing layer 26 is typically a polymer, and preferably is an adhesive polymer that can help attach the ceramic tiles 12 to the carrier sheet 16. Suitable polymers include shock absorbing polymers such as elastomer (e.g., rubber), an epoxy, a thermoplastic polymer, or a thermosetting polymer, with polyurethane adhesives such as various urethane adhesives provided by LORD® (e.g., LORD 7542A or 7545 urethane adhesives) being preferred. While visco-elastic polymer adhesives that form a shock absorbing layer are preferred, non-shock absorbing polymer adhesives may also be used. When adhesive is used, an appropriate amount of adhesive is applied to either the back surface of the ceramic tiles 12 or to the front surface 18 of the carrier sheet 16, and the two are then bonded together.

Mechanical fasteners 28 can also be used to attach the ceramic tiles 12 to the to carrier sheet 16. A wide variety of suitable mechanical fasteners 28 are known, including bolts, screw, rivets, and pins, and can be made of metal (e.g., steel, brass, aluminum) or a hard plastic. Use of snap or blind rivets readily allow the ceramic tiles 12 to be attached to the carrier sheet 16 without having to access the mechanical fastener 28 through the ceramic tile 12. A wide variety of different types of snap rivets may be used, including, for example, snap rivets with an arrow shank, a click-lock shank, or a ratcheting shank. Suitable mechanical fasteners can be obtained from McMaster-Carr®, or various other suppliers. Both reusable and non-reusable mechanical fasteners 28 can be used, though reusable mechanical fasteners may be preferred for some uses as they facilitate the replacement of damaged ceramic tiles 12. The rivet base 34 can be secured in the carrier sheet 16, as shown in FIG. 1.

As an example of the type of mechanical fastener 28 that can be used, a dovetail shank fastener is shown in FIG. 3, which provides an exploded perspective view of a mechanical fastener 28. This type of mechanical fastener 28 includes two halves, the male section 30 and the female section 32. The male section 30 includes a rivet base 34 supporting a rivet shank 36 that bears a rivet head 38. The rivet shank 36 and rivet head 38 fit within the female section 32 which includes a receiving column 40 that is mounted on a column base 42. Within the column 40 is a retainer 44, which acts to hold the rivet head 38 in place once it has been inserted. For example, the retainer 44 may be a saw-toothed region within the column 40 that hooks around the edge of the rivet head 38 to prevent its withdrawal. By attaching the rivet base 34 and the column base 42 to the ceramic tile 12 and the carrier sheet 16, the mechanical fastener 28 will hold the two together. While the mechanical fastener 28 shown in FIG. 1 includes a male section 30 positioned on the carrier sheet 16 and a female section 32 positioned within the ceramic tile 12, it is readily apparent that these sections can be interchanged such that the male section 30 is within the ceramic tile 12 while the female section 32 is fixed to the carrier sheet 16.

The affixable armor sheet 10 can also include an adhesive layer 46. An adhesive layer 46 can be placed on the back surface 20 of the carrier sheet 16, where it can attach the affixable armor sheet 10 to a surface. The adhesive layer 46 may be formed using adhesive polymers such as those described for use in the tile backing layer 26. For example, the adhesive layer 46 can be formed with an elastomer (e.g., rubber), an epoxy, a thermoplastic polymer, or a thermosetting polymer. A preferred polymer for use in forming the adhesive layer 46 is polyurethane. While the adhesive layer 46 functions in part to attach the affixable armor sheet 10 to a surface, it may provide other functions as well. For example, the visco-elastic material used to form the adhesive layer 46 may help absorb the kinetic energy of projectile or blast impact in order to further protect the surface covered by the affixable armor sheet 10. Visco-elastic polymers, unlike fully elastic polymers, are permanently deformed as a result of impact, thus allowing greater energy to be absorbed and helping to minimize the damage resulting from projectile impact.

The affixable armor sheet 10 can also be attached to a surface by other methods. Mechanical means such as straps 48 may be used to attach one or more affixable armor sheets 10 to a surface. Straps 48 may be used as the sole means to attach one or more affixable armor sheets 10 to a surface, or they may be used in addition to the mechanical and/or adhesive forms of attachment already described. For example, an affixable armor sheet 10 can be mounted on a surface using straps 48 anchored from strap holders 50 mounted on the surface, as shown in FIG. 2. Sheet connectors 52 are used to either retain the affixable armor sheet 10 on the straps 48, and/or to connect adjacent affixable armor sheets 10, as illustrated in FIG. 4. Sheet connectors 52 may be clips or other suitable devices that can connect adjacent affixable armor sheets 10 or attach the sheets to the straps 48. For example, FIG. 4 shows two adjacent affixable armor sheets 10 that are connected using sheet connectors 52 that hook into sheet openings 54 (e.g., eyelets) provided within the carrier sheet 16.

The use of mechanical means to affix an affixable armor sheet 10 to a surface is further illustrated by FIG. 5, which provides a side view of a vehicle 22 bearing affixable armor sheets 10 mounted to the vehicle by straps 48. The vehicle 22 includes a number of strap holders 50 positioned in pairs of first and second strap holders 50 over the surface of the vehicle 22. Straps 48 are then attached to the first and second step holders 50 of a strap holder pair. By appropriately spacing the pairs of strap holders 50 over the surface of the vehicle 22 (i.e., with spacing equal to the length of the affixable armor sheets 10), a number of affixable armor sheets 10 can be attached the surface of the vehicle 22. While FIG. 5 shows a pair of straps 48 for each of the affixable armor sheets 10, fewer straps 48 can be used. For example, a plurality of adjacent affixable armor sheets 10 can be attached using sheet connectors 52, and then providing a strap 48 supported by first and second strap holders 50 at each end of the plurality of adjacent affixable armor sheets 10. As shown in FIG. 5, affixable armor sheets 10 may be provided over particularly valuable sections of the vehicle 22, such as the doors 56 or the cargo section 58.

Alternately, the ceramic tiles 12 may be affixed directly to a surface; i.e., without first placing them on a carrier sheet 16. The ceramic tiles 12 can be directly affixed to a surface using either an adhesive polymer or mechanical fasteners 28, or both. If mechanical fasteners 28 are used, the mechanical fastener 28 is directly attached to the surface rather than being attached to a carrier sheet 16. For example, if a mechanical fastener 28 such as that shown in FIG. 3 is used, the rivet base 34 of the male section 30 can be attached to the surface using soldering or an adhesive, while the female section 32 is attached within the ceramic tile 12. The ceramic tile 12 can then be directly attached to the surface by connecting the male section 30 with the female section 32 of the mechanical fastener 28. If an adhesive polymer is used alone or together with a mechanical fastener, the adhesive polymer can be a visco-elastic adhesive polymer to provide additional protection against projectile impact.

The affixable armor sheet 10 of the invention includes a plurality of polygonal ceramic tiles 12. FIGS. 6A and 6B provide top perspective and bottom perspective views, respectively, of a polygonal ceramic tile 12. Because the ceramic tiles 12 are polygonal, they include multiple tile sides 60. The ceramic tiles 12 may include both a tile base 62 and a deflecting front surface 64. The tile base 62 is the portion of the ceramic-tile 12 that is typically adjacent to the carrier sheet 12, although there may be an intervening tile backing layer 26. The tile base 62 may have a width from about 30 to about 60 mm. The tile base 62 is preferably shaped to allow the adjacent polygonal ceramic tiles 12 to form a layer that may or may not include a defined gap 14 between the ceramic tiles 12. The tile base 62 preferably has a perimeter that forms a simple polygon (e.g., a triangle, square, or hexagon) that allows the ceramic tiles 12 to be placed in a repeating pattern with potentially very little gap between adjacent tiles 12. For example, use of ceramic tiles 12 with a hexagonal perimeter allows multiple adjacent ceramic tiles 12 to form a layer with a honeycomb pattern.

The tile base 62 of the polygonal ceramic tile 12 is typically flat. However, in some embodiments, the tile base 62 can be concave or include a cavity 66. Providing a concave or cavity-including tile base 62 provides the advantage of reducing the overall weight of the ceramic tile 12 relative to a tile without the concave side or cavity, and may also be used to facilitate incorporation of a mechanical fastener 28 into the ceramic tile 12. The cavity has also been formed to greatly reduce the damage to the rest of the armor solution, vehicle body and adjacent tiles through the mechanical advantage of allowing the impact area to fold/crush in upon itself imploding to absorb the shattered material on the smallest space possible. The cavity 66 may have an arch or dome shape to provide additional structural support for the ceramic tile 12.

The side of the polygonal ceramic tile 12 that faces towards a potential incoming projectile provides a deflecting front surface 64. The deflecting front surface 64 of the ceramic tile 12 has a shape that encourages the redirection of an incoming projectile from its initial flight path. Preferably, the deflecting front surface 64 has a non-spherical configuration. For example, the deflecting front surface 64 may be conical, pyramidal, or wedge-shaped in order to provide angled surfaces that tend to redirect an incoming projectile so that the new, redirected path is at a non-perpendicular angle (i.e., an oblique angle) relative to the plane formed by the layer of adjoining ceramic tiles 12. The angle of inclination provided by the deflecting front surface 64 preferably ranges from about 10 degrees to about 30 degrees. It is also preferable that the angled surface provided by the deflecting front surface 64 be rounded to decrease or eliminate points or edges that would otherwise be present on the surface. Preferably, an incoming projectile is blunted or shattered by impact with a polygonal ceramic tile 12.

The tile sides 60 of the ceramic tile 12 may require extra thickness to defeat a projectile. In such a case, the deflecting front surface 64 may flare upwards adjacent to the tile sides 60 of the tile 12, providing a front surface 64 with a flared perimeter. FIGS. 7A and 7B provide cross-sectional and a top perspective views, respectively, of a polygonal ceramic tile 12 that includes a flared perimeter. A ceramic tile 12 that flares upwards along the tile sides 60 will include a ridge 68 that runs around the perimeter of deflecting front surface 64 the ceramic tile 12, creating a trough 72 (e.g., a depression or swale) between the tile sides 60 of the ceramic tile 12 and the central conical or pyramidal section 70. The ridge 68 increases the strength of the sides of the ceramic tiles.

The ridge 68 shown in FIGS. 7A and 7B provides extra thickness at the edges and corners that otherwise might provide less resistance to an incoming projectile. A deflecting front surface 64 provided with a flared perimeter ridge 68 will thus include two basic features; a central conical or pyramidal section 70 (e.g., a frustrum of a cone or pyramid) in the middle portion of the ceramic tile 12, and a flared perimeter ridge 68 that runs around the perimeter of the deflecting front surface 64. The flared perimeter ridge 68 of the deflecting front surface 64 thus forms a thicker rim along outer edges of the ceramic tile 12. The region between the central conical or pyramidal section 70 and the flared perimeter ridge 68 creates a trough 72 between the center of the tile and the tile edges. The base of the trough 72 will correspond to the minimum thickness of the ceramic tile 12. When this trough 72 is in a plane parallel to the tile base 62, it will not offer as high a probability for deflection for a projectile directly impacting the trough 72. Thus, it may be preferable to create irregularity in the surface of the trough 72. For example, the surface of the trough 72 may be allowed to move up or down (undulation) with respect to the plane corresponding the average minimum thickness. This design allows all surfaces to be curved with respect to the direction of the incoming projectile. In particular, the trough 72 may include alternating ridges; i.e., regular or irregular hills and valleys that alternate around its circumference. These hills or ridges may be perpendicular to a tangent off of the trough 72, or they may be less than perpendicular, as in the case of hills and ridges formed by a spiral pattern of hills and troughs that extend from the center of the deflecting front surface 64 through the trough 72.

The ceramic tiles 12 should have a thickness that is sufficient to shatter the projectile and deflect fragments. This thickness is determined by the specific nature of the threat the armor is expected to face, as well as composition, density, mechanical properties, geometry of the ceramic and its shape. The ceramic tiles 12 can be prepared using a variety of suitable ceramic materials. Suitable ceramic materials are preferably light (density less than 4 gm/cc), hard (e.g., hardness preferably greater than that of tungsten carbide), and possess high compressive strength. When a ceramic tile 12 sustains a ballistic impact, the face of the tile experiences high compressive force. Due to their high compressive strength, the ceramic material resists compression upon projectile impact, and erosion of the projectile tip occurs first instead, followed by failure of the ceramic in tension as the compressive shock wave reaches the back surface of the tile and is reflected as a tensile wave. By the time the ceramic fails, it has absorbed energy and has eroded the tip of the projectile so that the projectile cannot easily penetrate the protected surface.

Examples of ceramic materials that are suitable for use in forming ceramic tiles 12 are aluminum oxide, zirconia toughened alumina, precipitation strengthened alumina, magnesium oxide, SiAlON (Silicon oxy-nitride) silicon carbide, silicon nitride, silicon oxide, boron carbide, aluminum borides, and boron nitride, titanium diboride or more generally from a group of oxides, boride, carbides, nitrides of alkaline earth, Group IIA, IIIB, IVB and transition metals and mixtures thereof. In addition, metal matrix composite containing ceramic phase are also suitable. Suitable ceramic tiles can be prepared according to methods known to those skilled in the art, such as by compression molding and sintering or hot pressing.

Density of the ceramic material is a very important factor in determining its strength. For example, alumina ceramic material is formed into ceramic tiles 12 that have a density greater than 3.5 grams (g)/cubic centimeter (cc), with density ranging from 3.8 g/cc to 3.97 g/cc (or between 95 and 99.9% of theoretical density) are preferred. Other ceramic materials' densities are even lower than that of alumina. For instance, relatively pure (>99%) SiC has a density of about 3.2 g/cc and boron carbide has density even lower than that of SiC which is about 2.8 g/cc. Therefore, there are several options to reduce areal densities of armor well below the critical areal density of typical vehicle armor such as hardened steel.

Further protection can be achieved by incorporating an energy absorbing material such a visco-elastic polyurethane that encloses the ceramic tiles 12. This enclosing layer is referred to herein as the retaining polymer 74, and may be used to encase the ceramic tiles 12. As used herein, the term “encase” means that a significant portion of the ceramic tiles 12 are in contact with the retaining polymer 74. Preferably, the retaining polymer 74 also flows into gaps 14 provided between the adjacent polygonal ceramic tiles 12. In some embodiments, the retaining polymer 74 may completely enclose the ceramic tiles 12, while in other embodiments portions of the tiles may be exposed or covered by other materials. A variety of polymers are suitable for use in forming the retaining polymer 74. The retaining polymer 74 can be any suitable material that retains elasticity upon hardening at the thickness used, such as an elastomer (e.g., rubber), an epoxy, a thermoplastic polymer, or a thermoset plastic. A preferred polymer for use in forming the retaining polymer 74 is polyurethane and its derivatives (e.g, visco-elastic polyurethane and polyurethane elastomers belonging to the family of materials described in U.S. Pat. No. 7,078,443, issued to Milliren, which is hereby incorporated by reference herein.

As described herein, the ceramic tiles 12 can be spaced apart to provide gaps 14 between them. While too large a gap 14 might allow a projectile to penetrate the armor without impacting a ceramic tile 12, the presence of a gap 14 tends to decrease the number of tiles that are fractured by a single impact. The gap 14 can be open, or it can be filled with suitable non-ceramic material such as a retaining polymer 74.

In some embodiments, the gaps 14 between the ceramic tiles 12 have a width that is less than the diameter of the expected ballistic threat, and may aid in decreasing damage to a vehicle or other protected structure by a ballistic threat. Preferably, the gap 14 has a diameter with a width that is less than half the diameter of an expected ballistic threat. The size of the gap 14 may be varied to account for the type of fire that the armor is expected to face. For example, the affixable armor sheet 10 may include gaps between adjacent ceramic tiles 12 with a width of 2 millimeters or less. A gap 14 with a width in this range would provide enhanced protection to projectiles ranging from typical small arms fire to 30 mm rounds. Alternately, if the primary expected threat is small arms fire only, gaps with a width of less than or equal to 0.25 millimeters may be preferred.

In embodiments of the invention using ceramic tiles 12 that include a cavity 66, the cavity 66 may include a fire retarding material to enhance the ability of the composite armor to absorb blast energy. For example, the fire retarding material may be fire-retarding particles. Fire-retarding particles can be relatively small pieces of material that absorb energy upon heating in order to help mitigate the effects of blast or other forms of energy release into the ceramic tiles 12. The fire-retarding particles can include water-containing materials that help absorb energy by taking advantage of the relatively high specific heat (C_(v)H=74.539 J mol⁻¹K⁻¹ (25° C.)) of liquid water.

Examples of material that may be used in fire-retarding particles includes alumina or magnesia hydrate, zinc borate, perlite and vermiculite. Perlite is an amorphous volcanic glass composed primarily of silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃) that softens and releases water when it reaches temperatures of 850-900° C., expanding to 7-16 times its original volume. Vermiculite is a mineral with the formula (MgFe,Al)₃(Al,Si)₄O₁₀(OH)₂.4H₂O that also expands significantly upon application of heat. In addition to including water, both of these materials expand substantially upon being heated. In addition to absorbing additional energy, expansion of the fire-retarding particles can minimize damage to the ceramic tiles 12 resulting from blast or projectile impact. Alternately, or in addition, the fire retarding material included within the cavity 66 may include additional materials such as liquids (e.g., water) that have a high capacity for absorbing energy. Fragmentation of the ceramic tile 12 by projectile impact will result in an ultra-fine dispersion of fire suppressant liquid, which will effectively quench blast energy such as that produced by a fire ball.

Each one of the affixable armor sheets 10 can be cut along the edges to provide coverage of a complex shape. The affixable armor sheets 10 are typically positioned on a relatively flat surface. However, if one or more affixable armor sheets 10 are placed adjacent to or over a bend in the surface, an exposed edge can result. The bend is the angled region of the surface that results from two intersecting surfaces meeting, and will generally form either a right angle or an obtuse angle within the surface. The opening is the area over the exposed edge, and will be larger for angles from about 90° to about 135°. The bend and the resulting opening in the armor protection can be protected with a special gap-filling ceramic tile 76 that will fit in the reflex angle generated outside the bend, as shown in FIG. 8. The gap-filling ceramic tile 76 can be formed from the same types of materials used to form the polygonal ceramic tiles 12.

The gap-filling ceramic tile 76 has a first and second bonding edge 78 with a surface configured to match that of the tile sides 60 of the polygonal ceramic tile 12. The gap-filling ceramic tile 76 typically has an arch shape overall, with the bonding edges 78 forming the ends of the arch. The bonding edges 78 at the ends of the arch will form an angle with a degree that combines with the angle of the bend to provide a total of 180 degrees. For example, if the bend on the surface has an angle of 135°, the angle formed between the two bonding edges should be 45°. Thus, depending on the angle of the bend in the surface, the angle of the bonding edges 78 is generally from about 11 to about 90°. The gap-filling ceramic tile 76 is preferably fixed in position with an adhesive polymer that is applied between the bonding edges 78 of the gap filling ceramic tile 76 and the adjacent sides of the polygonal ceramic tiles 12.

If the opening is formed at the intersection of two adjacent affixable armor sheets 10, the gap-filling ceramic tile 76 is positioned between the two affixable armor sheets 10 and over the intersection of the two surfaces where the bend occurs. In addition, if an affixable armor sheet 10 with a flexible carrier sheet 16 is used, the affixable armor sheet 10 can be positioned over a bend in the surface. While the surface in this case will be partially protected by the carrier sheet 16, an opening in the protection provided by the ceramic tiles 12 can still result, thus making it desirable to position one or more gap-filling ceramic tiles 76 between the ceramic tiles 12 within the affixable armor sheet 10 along the line where the carrier sheet 16 bends.

The present invention provides an affixable armor sheet that can be attached to any existing surface in order to provide additional protection. For example, the affixable armor sheet 10 can be used to provide protection for vehicles, crafts, buildings, and personnel. The affixable armor sheet 10 may be integrated into the vehicle or structure when it is originally built, or may be provided later as an “add-on.” When provided as an add-on, the affixable armor sheet armor 10 will be provided with clips and hinges or brackets (or other suitable fittings), typically on the carrier sheet 16, to allow the affixable armor sheet 10 to be placed on a vehicle where it can protect the vehicle and/or its occupants from blast and ballistic threats. For example, the affixable armor sheet 10 may be fitted to be placed over a vehicle door 56, or placed on a vehicle underbody. In particular, the affixable armor sheet 10 is suited for placement on light military vehicles such as the HMMWV that might not otherwise have sufficient protection against heavy caliber ammunition or IEDs. Adding affixable armor to a surface quickly upgrades existing hardware by providing increased protection against projectile threats. Furthermore, by varying the thickness of the ceramic tiles 12 or other components, it can be tailored to meet varying levels of threat.

The affixable armor sheet 10 provides protection against a variety of blast and ballistic threats. For example, the affixable armor is capable of preventing penetration by 0.50 caliber armor piercing incendiary steel core projectiles fired at a velocity of 2500-2700 feet/sec, as well as 20 mm fragment simulation projectiles (FSP) fired at a velocity of 3600 feet/sec. The 20 mm FSP round corresponds to size and kinetic energy of over 90% of the fragments originating from a 152 mm Russian artillery shell detonated at about 2 meters, which represents a typical IED threat or other nearby artillery blast.

Another advantage of the affixable armor sheet 10 is that it can be readily removed from a surface. For example, after damage is sustained from an IED or other projectile threat, the one or more affixable armor sheets 10 that have sustained damage can be removed. This can be accomplished by unclipping the affixable armor sheet 10 from adjacent sheets by removing the appropriate sheet connectors 52 and then removing the affixable armor sheet 10 from the surface. The damaged area and a part of adjacent area can then be removed by appropriate tools such as a small crowbar or a chisel. Alternately, individual ceramic tiles 12 that are part of an affixable armor sheet 10 or are directly attached to a surface can also be replaced. For example, if individual ceramic tiles 12 have been attached to a surface using mechanical fasteners 28, the older, damaged ceramic tiles 12 can be removed and new ceramic tiles 12 placed onto the old mechanical fasteners 28. If the old fastener is damaged, either a new fastener can be attached or the entire damaged area that is attached to vehicle surface can be removed so that a new affixable armor sheet 10 can be attached to the surface.

Several embodiments of the present invention are illustrated by the following example. It is to be understood that the particular example, materials, amounts, and procedures are to be interpreted broadly in accordance with the scope of the invention as set forth herein.

EXAMPLE Example 1

One example of the present invention is illustrated by an affixable armor sheet 10 referred to by the trade name CERASHOT™. CERASHOT™ armor is an up-armor solution useful for operating units that they can apply it in-country to vehicles using tactical unit personnel, in zone, and defeat 0.50 Caliber armor piercing (M2) ammunition (and equivalent threats) starting from nothing more than the unarmored skin of HMMWVs, 2.5 & 5 Ton Trucks, and light personnel carriers including civilian SUVs.

CERASHOT™ armor is a 1′×1′ square sheet of 36 specially shaped ceramic tiles weighing 18 lbs attached to a self adhesive backing. The tiles used in CERASHOT™ armor, and a 1′×1′ armor sheet with a number of tiles affixed are shown in FIG. 2. Each sheet can be peeled and placed on a typical vehicle skin (ie: unarmored HUMMWV door) in order to provide full protection of occupants against 0.50 Caliber ballistic threats. Each vehicle receives 50 to 250 square feet of CERASHOT™ armor for Crew Cab protection (ie: 1800 lbs on a M1151A1 HMMWV @50 square feet (sqr-ft) requiring not more than 2 service personnel for 4 hours). When damaged, individual tiles and sheets can be rapidly removed and replaced with a new vehicle skin conforming sheet either in the tactical environment or back at the Level 10/20 maintenance area. CERASHOT™ armor provides threat protection against 5.56 mm, 7.62 mm small arms, 50 Caliber armor piercing and armor piercing incendiary ammunition, Multi-shot >50 mm caliber shots spaced at 2″ (or more) apart, IED simulated by 20 mm FSP @3600 FPS, NATO STANAG 4569 L3, and others, depending on tile thickness.

CERASHOT™ armor includes an oblique deflection-shaped tile face, a hollow tile back, incendiary damping liquid cells (up kit as required), and “man-mountable”, self-adhesive, sheets for tactical application and repair down to 10/20 Level (or equivalent). As noted, CERASHOT™ armor may be supplied in kits. These kits may be used for HMMWV, where they supply protection for various amounts of surface area (e.g., 50, 150, 250 sqr-ft). For example, kits for a 2.5 Ton trucks supply 50 sqr-ft protection, for 5 Ton trucks they supply 100 sqr-ft protection, for F-Series pick-up vehicles they supply protection for 50, 150, or 250 sqr-ft, and for SUVs where they also supply protection for 50, 150, or 250 sqr-ft. In addition, further kits are available that provide replacement tiles (3 sqr-ft/box), 25 specially shaped “trim” pieces (i.e., gap-filling ceramic tiles), and fire suppression material (3 sqr-ft/box).

The complete disclosure of all documents such as patents, patent applications, and publications cited herein are incorporated by reference. While various embodiments in accordance with the present invention have been shown and described, it is understood the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modifications as encompassed by the scope of the appended claim. 

1. An affixable armor sheet, comprising: a plurality of adjacent polygonal ceramic tiles comprising a base, sides, and a substantially conical or pyramidal deflecting front surface; a carrier sheet with a front side and a back side; and attachment means for attaching the base of the polygonal ceramic tiles to the front side of the flexible carrier sheet.
 2. The affixable armor sheet of claim 1, wherein the back side of the carrier sheet includes an adhesive.
 3. The affixable armor sheet of claim 1, wherein the attachment means comprise an adhesive.
 4. The affixable armor sheet of claim 1, wherein the attachment means comprise a mechanical fastener.
 5. The affixable armor sheet of claim 1, wherein the ceramic tiles are encased in a retaining polymer.
 6. The affixable armor sheet of claim 1, wherein the ceramic tiles include a cavity containing a fire-retarding material.
 7. The affixable armor sheet of claim 1, wherein a shock absorbing material is provided on the base of the ceramic tiles.
 8. The affixable armor sheet of claim 1, wherein the deflecting front surface of the ceramic tiles includes a ridge that flares upwards above the sides of the ceramic tiles.
 9. The affixable armor sheet of claim 1, wherein the ceramic tiles are spaced apart by a gap with a width that is substantially less than the diameter of an expected ballistic threat.
 10. The affixable armor sheet of claim 9, wherein the gap has a width of less than 2 millimeters.
 11. The affixable armor sheet of claim 9, wherein the gap has a width of less than or equal to 0.25 millimeters.
 12. The affixable armor sheet of claim 1, wherein an affixable armor sheet is placed on each of two surfaces that meet at an angle, and one or more gap-filling ceramic tiles are positioned between the two affixable armor sheets and over the intersection of the two surfaces.
 13. A composite armor sheet comprising: a layer of adjacent polygonal ceramic tiles comprising a base, sides, and a front surface encased in a retaining polymer positioned over a carrier sheet, wherein the ceramic tiles are spaced apart by a gap with a width that is less than the diameter of an expected ballistic threat.
 14. The composite armor sheet of claim 13, wherein the gap has a width that is less than half the diameter of the expected ballistic threat.
 15. The composite armor sheet of claim 13, wherein the gap has a width of less than 2 millimeters.
 16. The composite armor sheet of claim 13, wherein gap has a width of less than or equal to 0.25 millimeters.
 17. The composite armor sheet of claim 13, wherein the ceramic tiles have a non-spherical deflecting front surface to shatter and disrupt hardened and explosively formed projectiles earlier in impact than flat tiles further from vehicle in same or less weight than competitive flat tiles.
 18. The composite armor sheet of claim 17, wherein a portion of the deflecting front surface of the ceramic tiles is substantially conical or pyramidal.
 19. The composite armor sheet of claim 17, wherein the deflecting front surface of the ceramic tiles includes a ridge that flares upwards above the sides of the ceramic tiles to deflect shattered particles away from the armor and the vehicle.
 20. The composite armor sheet of claim 19, wherein the ridge increases the strength of the sides of the ceramic tiles.
 21. The composite armor sheet of claim 13, wherein the ceramic tiles include a cavity positioned on the back of the ceramic tile that deforms upon projectile impact to decrease damage to the vehicle and/or adjacent ceramic tiles.
 22. The composite armor sheet of claim 13, wherein the ceramic tiles include a cavity containing a fire-retarding material. 